diff --git a/src/bias/PBMetaD.cpp b/src/bias/PBMetaD.cpp
index 0d37798e01f45667071bd32ea397306d8495ef5c..e3d558d334c3db958e260de3ccaae5e430a5ad72 100644
--- a/src/bias/PBMetaD.cpp
+++ b/src/bias/PBMetaD.cpp
@@ -228,7 +228,7 @@ private:
     Gaussian(const vector<double> & center,const vector<double> & sigma, double height, bool multivariate):
       center(center),sigma(sigma),height(height),multivariate(multivariate),invsigma(sigma) {
       // to avoid troubles from zero element in flexible hills
-      for(unsigned i=0; i<invsigma.size(); ++i) if(abs(invsigma[i])>1.e-20) invsigma[i]=1.0/invsigma[i] ; else invsigma[i]=0.0;
+        for(unsigned i=0; i<invsigma.size(); ++i) if(abs(invsigma[i])>1.e-20) invsigma[i]=1.0/invsigma[i] ; else invsigma[i]=0.0;
     }
   };
   vector<double> sigma0_;